Six weeks ago Nick Tonkin posted a message on the modperl mailing list asking for used copies of Learning Perl for a class he’d be teaching to disadvantaged kids. I emailed him back about a copy of the Perl Cookbook I had but hadn’t used in a while, and he said “Send it on!” and thanked me warmly.
I figured that was that, good karma and all. But today I get back from my wife's holiday party -- teachers are so catty! :-) -- and I have six emails with subjects like "gracias por los libros" and "hi thanks for the book!!!!!!!" Not only that, but a few of the students included the Perl code they used to generate the emails. Awesome! (And to think I almost deleted a few because of the similarity to spam subjects...)